diff --git a/monitor.c b/monitor.c
index 36c79538b..702576820 100644
--- a/monitor.c
+++ b/monitor.c
@@ -93,6 +93,18 @@ monitor_get_session(struct monitor_set *ms)
 	return (s);
 }
 
+/* Create a format tree for a subscription. */
+static struct format_tree *
+monitor_create_formats(struct client *c, struct session *s, struct winlink *wl,
+    struct window_pane *wp)
+{
+	struct format_tree	*ft;
+
+	ft = format_create(NULL, NULL, FORMAT_NOJOBS, 0);
+	format_defaults(ft, c, s, wl, wp);
+	return (ft);
+}
+
 /* Compare subscriptions. */
 static int
 monitor_item_cmp(struct monitor_item *m1, struct monitor_item *m2)
@@ -236,7 +248,7 @@ monitor_check_pane(struct monitor_set *ms, struct monitor_item *me)
 		if (wl->session != s)
 			continue;
 
-		ft = format_create_defaults(NULL, c, s, wl, wp);
+		ft = monitor_create_formats(c, s, wl, wp);
 		value = format_expand(ft, me->format);
 		format_free(ft);
 
@@ -314,7 +326,7 @@ monitor_check_window(struct monitor_set *ms, struct monitor_item *me)
 		if (wl->session != s)
 			continue;
 
-		ft = format_create_defaults(NULL, c, s, wl, NULL);
+		ft = monitor_create_formats(c, s, wl, NULL);
 		value = format_expand(ft, me->format);
 		format_free(ft);
 
@@ -382,7 +394,7 @@ monitor_check_sessions(struct monitor_set *ms)
 	struct monitor_item	*me, *me1;
 	struct format_tree	*ft;
 
-	ft = format_create_defaults(NULL, c, s, NULL, NULL);
+	ft = monitor_create_formats(c, s, NULL, NULL);
 	RB_FOREACH_SAFE(me, monitor_items, &ms->items, me1) {
 		if (me->type == MONITOR_SESSION)
 			monitor_check_session(ms, me, ft);
@@ -427,7 +439,7 @@ monitor_check_all_panes(struct monitor_set *ms)
 		ms->generation = 1;
 	RB_FOREACH(wl, winlinks, &s->windows) {
 		TAILQ_FOREACH(wp, &wl->window->panes, entry) {
-			ft = format_create_defaults(NULL, c, s, wl, wp);
+			ft = monitor_create_formats(c, s, wl, wp);
 			RB_FOREACH_SAFE(me, monitor_items, &ms->items, me1) {
 				if (me->type != MONITOR_ALL_PANES)
 					continue;
@@ -455,7 +467,7 @@ monitor_check_all_windows(struct monitor_set *ms)
 	if (++ms->generation == 0)
 		ms->generation = 1;
 	RB_FOREACH(wl, winlinks, &s->windows) {
-		ft = format_create_defaults(NULL, c, s, wl, NULL);
+		ft = monitor_create_formats(c, s, wl, NULL);
 		RB_FOREACH_SAFE(me, monitor_items, &ms->items, me1) {
 			if (me->type != MONITOR_ALL_WINDOWS)
 				continue;
diff --git a/regress/alerts.sh b/regress/alerts.sh
index 7a39ddefc..cfb84c711 100644
--- a/regress/alerts.sh
+++ b/regress/alerts.sh
@@ -19,7 +19,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/am-terminal.sh b/regress/am-terminal.sh
index bf1cabfe7..fae0e502d 100644
--- a/regress/am-terminal.sh
+++ b/regress/am-terminal.sh
@@ -4,9 +4,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX2 kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/border-arrows.sh b/regress/border-arrows.sh
index ea571b05a..a67171bf5 100644
--- a/regress/border-arrows.sh
+++ b/regress/border-arrows.sh
@@ -11,9 +11,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX_OUTER="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX_OUTER="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX_OUTER kill-server 2>/dev/null
 
 trap "$TMUX kill-server 2>/dev/null; $TMUX_OUTER kill-server 2>/dev/null" 0 1 15
diff --git a/regress/buffers.sh b/regress/buffers.sh
index 0b3267610..fdacacb5b 100644
--- a/regress/buffers.sh
+++ b/regress/buffers.sh
@@ -23,7 +23,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/capture-pane-hyperlink.sh b/regress/capture-pane-hyperlink.sh
index 80092e7f2..ec89c6c5d 100644
--- a/regress/capture-pane-hyperlink.sh
+++ b/regress/capture-pane-hyperlink.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 TMP=$(mktemp)
 TMP2=$(mktemp)
 trap "rm -f $TMP $TMP2" 0 1 15
diff --git a/regress/capture-pane-sgr0.sh b/regress/capture-pane-sgr0.sh
index 7c9c32315..1e73e7191 100644
--- a/regress/capture-pane-sgr0.sh
+++ b/regress/capture-pane-sgr0.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/check-names.sh b/regress/check-names.sh
index 886299f2d..be8ad617b 100644
--- a/regress/check-names.sh
+++ b/regress/check-names.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 fail()
diff --git a/regress/choose-buffer.sh b/regress/choose-buffer.sh
index a10d161eb..ca9a26758 100644
--- a/regress/choose-buffer.sh
+++ b/regress/choose-buffer.sh
@@ -20,8 +20,8 @@ TERM=screen
 TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
@@ -52,7 +52,7 @@ wait_for()
 	i=0
 	while [ "$i" -lt 50 ]; do
 		CAPTURED=$(capture)
-		if echo "$CAPTURED" | grep -q "$1"; then
+		if printf '%s\n' "$CAPTURED" | grep -F -q "$1"; then
 			return 0
 		fi
 		sleep 0.2
@@ -61,6 +61,23 @@ wait_for()
 	fail "timed out waiting for '$1'"
 }
 
+# wait_gone $marker
+#
+# Wait (up to ~10s) until the rendered screen no longer contains $marker.
+wait_gone()
+{
+	i=0
+	while [ "$i" -lt 50 ]; do
+		CAPTURED=$(capture)
+		if ! printf '%s\n' "$CAPTURED" | grep -F -q "$1"; then
+			return 0
+		fi
+		sleep 0.2
+		i=$((i + 1))
+	done
+	fail "timed out waiting for '$1' to disappear"
+}
+
 # wait_count $marker $n
 #
 # Wait (up to ~10s) until exactly $n rendered lines contain $marker. The
@@ -70,7 +87,7 @@ wait_count()
 	i=0
 	while [ "$i" -lt 50 ]; do
 		CAPTURED=$(capture)
-		c=$(echo "$CAPTURED" | grep -c "$1")
+		c=$(printf '%s\n' "$CAPTURED" | grep -F -c "$1")
 		[ "$c" -eq "$2" ] && return 0
 		sleep 0.2
 		i=$((i + 1))
@@ -129,11 +146,15 @@ wait_mode()
 
 exit_mode()
 {
+	marker=$1
+	shift
+
 	$TMUX send-keys -t aaa:0 "$@" || fail "send-keys $* failed"
 	wait_mode aaa:0 0
+	wait_gone "$marker"
 }
 
-$TMUX new-session -d -s aaa -x 80 -y 24 || exit 1
+$TMUX new-session -d -s aaa -x 80 -y 24 'cat' || exit 1
 
 $TMUX2 new-session -d -s out -x 80 -y 24 "$TMUX attach -t aaa" || exit 1
 wait_clients 1 || fail "no client attached to test server"
@@ -146,28 +167,36 @@ $TMUX set-buffer -b bufz "other buffer" || exit 1
 $TMUX choose-buffer -t aaa:0 -F 'B1' -f '#{==:#{buffer_name},bufa}' || exit 1
 wait_count ': B1' 1
 out=$CAPTURED
-echo "$out" | grep -q 'bufa: B1' || fail "bufa missing when it matches"
-echo "$out" | grep -q 'bufz: B1' && fail "bufz shown but does not match"
-[ "$(echo "$out" | grep -c ': B1')" -eq 1 ] || fail "expected 1 buffer"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'bufa: B1' || \
+	fail "bufa missing when it matches"
+printf '%s\n' "$out" | grep -F -q 'bufz: B1' && \
+	fail "bufz shown but does not match"
+[ "$(printf '%s\n' "$out" | grep -F -c ': B1')" -eq 1 ] || \
+	fail "expected 1 buffer"
+exit_mode ': B1' q
 
 # --- filter by buffer content ------------------------------------------------
 $TMUX choose-buffer -t aaa:0 -F 'B2' -f '#{m:*hello*,#{buffer_sample}}' || \
 	exit 1
 wait_count ': B2' 1
 out=$CAPTURED
-echo "$out" | grep -q 'bufa: B2' || fail "bufa missing when content matches"
-echo "$out" | grep -q 'bufz: B2' && fail "bufz shown but content not matched"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'bufa: B2' || \
+	fail "bufa missing when content matches"
+printf '%s\n' "$out" | grep -F -q 'bufz: B2' && \
+	fail "bufz shown but content not matched"
+exit_mode ': B2' q
 
 # --- no filter shows both buffers ---------------------------------------------
 $TMUX choose-buffer -t aaa:0 -F 'B3' || exit 1
 wait_count ': B3' 2
 out=$CAPTURED
-echo "$out" | grep -q 'bufa: B3' || fail "bufa missing with no filter"
-echo "$out" | grep -q 'bufz: B3' || fail "bufz missing with no filter"
-[ "$(echo "$out" | grep -c ': B3')" -eq 2 ] || fail "expected 2 buffers"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'bufa: B3' || \
+	fail "bufa missing with no filter"
+printf '%s\n' "$out" | grep -F -q 'bufz: B3' || \
+	fail "bufz missing with no filter"
+[ "$(printf '%s\n' "$out" | grep -F -c ': B3')" -eq 2 ] || \
+	fail "expected 2 buffers"
+exit_mode ': B3' q
 
 # --- filter matching nothing ---------------------------------------------------
 #
@@ -176,25 +205,30 @@ $TMUX choose-buffer -t aaa:0 -F 'B4' -f '#{==:#{buffer_name},nosuch}' || \
 	exit 1
 wait_count ': B4' 2
 out=$CAPTURED
-echo "$out" | grep -q 'bufa: B4' || fail "bufa missing with no-match filter"
-echo "$out" | grep -q 'bufz: B4' || fail "bufz missing with no-match filter"
-echo "$out" | grep -q 'no matches' || fail "no matches indicator missing"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'bufa: B4' || \
+	fail "bufa missing with no-match filter"
+printf '%s\n' "$out" | grep -F -q 'bufz: B4' || \
+	fail "bufz missing with no-match filter"
+printf '%s\n' "$out" | grep -F -q 'no matches' || \
+	fail "no matches indicator missing"
+exit_mode ': B4' q
 
 # --- sort orders ---------------------------------------------------------------
 #
 # By name bufa sorts first and -r reverses.
 $TMUX choose-buffer -t aaa:0 -F 'B5' -O name || exit 1
 wait_count ': B5' 2
-echo "$CAPTURED" | grep ': B5' | head -1 | grep -q 'bufa: B5' || \
+printf '%s\n' "$CAPTURED" | grep -F ': B5' | head -1 | \
+	grep -F -q 'bufa: B5' || \
 	fail "bufa not first with -O name"
-exit_mode q
+exit_mode ': B5' q
 
 $TMUX choose-buffer -t aaa:0 -F 'B6' -O name -r || exit 1
 wait_count ': B6' 2
-echo "$CAPTURED" | grep ': B6' | head -1 | grep -q 'bufz: B6' || \
+printf '%s\n' "$CAPTURED" | grep -F ': B6' | head -1 | \
+	grep -F -q 'bufz: B6' || \
 	fail "bufz not first with -O name -r"
-exit_mode q
+exit_mode ': B6' q
 
 # --- d deletes the selected buffer --------------------------------------------
 #
@@ -203,9 +237,9 @@ $TMUX choose-buffer -t aaa:0 -F 'G1' -f '#{==:#{buffer_name},bufz}' || exit 1
 wait_for 'bufz: G1'
 $TMUX send-keys -t aaa:0 d
 wait_buffers 1
-$TMUX list-buffers -F '#{buffer_name}' | grep -q 'bufa' || \
+$TMUX list-buffers -F '#{buffer_name}' | grep -F -q 'bufa' || \
 	fail "wrong buffer deleted"
-exit_mode q
+exit_mode ': G1' q
 
 # --- C-t tags all buffers and D deletes the tagged ------------------------------
 $TMUX set-buffer -b bufz "other buffer" || exit 1
@@ -214,7 +248,8 @@ $TMUX choose-buffer -t aaa:0 -F 'G2' || exit 1
 wait_count ': G2' 3
 $TMUX send-keys -t aaa:0 C-t D
 wait_buffers 0
-exit_mode q
+wait_mode aaa:0 0
+wait_gone ': G2'
 
 # --- Enter runs the default command (paste-buffer) ------------------------------
 #
@@ -223,10 +258,11 @@ exit_mode q
 $TMUX set-buffer -b bufa "hello buffer" || exit 1
 $TMUX choose-buffer -t aaa:0 -F 'G3' || exit 1
 wait_count ': G3' 1
-exit_mode Enter
+exit_mode ': G3' Enter
 i=0
 while [ "$i" -lt 50 ]; do
-	$TMUX capture-pane -p -t aaa:0 | grep -q 'hello buffer' && break
+	$TMUX capture-pane -p -t aaa:0 | grep -F -q 'hello buffer' && \
+		break
 	sleep 0.2
 	i=$((i + 1))
 done
diff --git a/regress/choose-client.sh b/regress/choose-client.sh
index 9031f86bd..d325f5335 100644
--- a/regress/choose-client.sh
+++ b/regress/choose-client.sh
@@ -19,8 +19,8 @@ TERM=screen
 TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
@@ -51,7 +51,7 @@ wait_for()
 	i=0
 	while [ "$i" -lt 50 ]; do
 		CAPTURED=$(capture)
-		if echo "$CAPTURED" | grep -q "$1"; then
+		if printf '%s\n' "$CAPTURED" | grep -F -q "$1"; then
 			return 0
 		fi
 		sleep 0.2
@@ -60,6 +60,23 @@ wait_for()
 	fail "timed out waiting for '$1'"
 }
 
+# wait_gone $marker
+#
+# Wait (up to ~10s) until the rendered screen no longer contains $marker.
+wait_gone()
+{
+	i=0
+	while [ "$i" -lt 50 ]; do
+		CAPTURED=$(capture)
+		if ! printf '%s\n' "$CAPTURED" | grep -F -q "$1"; then
+			return 0
+		fi
+		sleep 0.2
+		i=$((i + 1))
+	done
+	fail "timed out waiting for '$1' to disappear"
+}
+
 # wait_count $marker $n
 #
 # Wait (up to ~10s) until exactly $n rendered lines contain $marker. The
@@ -69,7 +86,7 @@ wait_count()
 	i=0
 	while [ "$i" -lt 50 ]; do
 		CAPTURED=$(capture)
-		c=$(echo "$CAPTURED" | grep -c "$1")
+		c=$(printf '%s\n' "$CAPTURED" | grep -F -c "$1")
 		[ "$c" -eq "$2" ] && return 0
 		sleep 0.2
 		i=$((i + 1))
@@ -113,15 +130,19 @@ wait_mode()
 
 exit_mode()
 {
+	marker=$1
+	shift
+
 	$TMUX send-keys -t aaa:0 "$@" || fail "send-keys $* failed"
 	wait_mode aaa:0 0
+	wait_gone "$marker"
 }
 
 # One client attached to each of two sessions; the mode is displayed on the
 # client attached to aaa (in window 0 of the outer server) and the filters
 # tell the clients apart by their attached session.
-$TMUX new-session -d -s aaa -x 80 -y 24 || exit 1
-$TMUX new-session -d -s bbb -x 80 -y 24 || exit 1
+$TMUX new-session -d -s aaa -x 80 -y 24 'cat' || exit 1
+$TMUX new-session -d -s bbb -x 80 -y 24 'cat' || exit 1
 
 $TMUX2 new-session -d -s out -x 80 -y 24 "$TMUX attach -t aaa" || exit 1
 $TMUX2 new-window -d -t out: "$TMUX attach -t bbb" || exit 1
@@ -132,29 +153,38 @@ $TMUX choose-client -t aaa:0 -F 'C1=#{client_session}' \
 	-f '#{==:#{client_session},aaa}' || exit 1
 wait_count 'C1=' 1
 out=$CAPTURED
-echo "$out" | grep -q 'C1=aaa' || fail "aaa client missing when it matches"
-echo "$out" | grep -q 'C1=bbb' && fail "bbb client shown but does not match"
-[ "$(echo "$out" | grep -c 'C1=')" -eq 1 ] || fail "expected 1 client"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'C1=aaa' || \
+	fail "aaa client missing when it matches"
+printf '%s\n' "$out" | grep -F -q 'C1=bbb' && \
+	fail "bbb client shown but does not match"
+[ "$(printf '%s\n' "$out" | grep -F -c 'C1=')" -eq 1 ] || \
+	fail "expected 1 client"
+exit_mode 'C1=' q
 
 # --- filter keeping only the bbb client -------------------------------------
 $TMUX choose-client -t aaa:0 -F 'C2=#{client_session}' \
 	-f '#{==:#{client_session},bbb}' || exit 1
 wait_count 'C2=' 1
 out=$CAPTURED
-echo "$out" | grep -q 'C2=bbb' || fail "bbb client missing when it matches"
-echo "$out" | grep -q 'C2=aaa' && fail "aaa client shown but does not match"
-[ "$(echo "$out" | grep -c 'C2=')" -eq 1 ] || fail "expected 1 client"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'C2=bbb' || \
+	fail "bbb client missing when it matches"
+printf '%s\n' "$out" | grep -F -q 'C2=aaa' && \
+	fail "aaa client shown but does not match"
+[ "$(printf '%s\n' "$out" | grep -F -c 'C2=')" -eq 1 ] || \
+	fail "expected 1 client"
+exit_mode 'C2=' q
 
 # --- no filter shows both clients -------------------------------------------
 $TMUX choose-client -t aaa:0 -F 'C3=#{client_session}' || exit 1
 wait_count 'C3=' 2
 out=$CAPTURED
-echo "$out" | grep -q 'C3=aaa' || fail "aaa client missing with no filter"
-echo "$out" | grep -q 'C3=bbb' || fail "bbb client missing with no filter"
-[ "$(echo "$out" | grep -c 'C3=')" -eq 2 ] || fail "expected 2 clients"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'C3=aaa' || \
+	fail "aaa client missing with no filter"
+printf '%s\n' "$out" | grep -F -q 'C3=bbb' || \
+	fail "bbb client missing with no filter"
+[ "$(printf '%s\n' "$out" | grep -F -c 'C3=')" -eq 2 ] || \
+	fail "expected 2 clients"
+exit_mode 'C3=' q
 
 # --- filter matching nothing ------------------------------------------------
 #
@@ -163,10 +193,13 @@ $TMUX choose-client -t aaa:0 -F 'C4=#{client_session}' \
 	-f '#{==:#{client_session},nosuch}' || exit 1
 wait_count 'C4=' 2
 out=$CAPTURED
-echo "$out" | grep -q 'C4=aaa' || fail "aaa client missing with no-match filter"
-echo "$out" | grep -q 'C4=bbb' || fail "bbb client missing with no-match filter"
-echo "$out" | grep -q 'no matches' || fail "no matches indicator missing"
-exit_mode q
+printf '%s\n' "$out" | grep -F -q 'C4=aaa' || \
+	fail "aaa client missing with no-match filter"
+printf '%s\n' "$out" | grep -F -q 'C4=bbb' || \
+	fail "bbb client missing with no-match filter"
+printf '%s\n' "$out" | grep -F -q 'no matches' || \
+	fail "no matches indicator missing"
+exit_mode 'C4=' q
 
 # --- Enter runs the default command (detach-client) --------------------------
 #
@@ -178,6 +211,7 @@ wait_for 'G1=bbb'
 $TMUX send-keys -t aaa:0 Enter || fail "send-keys Enter failed"
 wait_clients 1 || fail "bbb client did not detach"
 wait_mode aaa:0 0
+wait_gone 'G1='
 [ "$($TMUX list-clients -F '#{client_session}')" = "aaa" ] || \
 	fail "wrong client detached"
 
diff --git a/regress/choose-tree.sh b/regress/choose-tree.sh
index b34cc2bd2..132890730 100644
--- a/regress/choose-tree.sh
+++ b/regress/choose-tree.sh
@@ -27,8 +27,8 @@ TERM=screen
 TMP=$(mktemp -d) || exit 1
 TMUX_TMPDIR="$TMP"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
@@ -59,7 +59,7 @@ wait_for()
 	i=0
 	while [ "$i" -lt 50 ]; do
 		CAPTURED=$(capture)
-		if echo "$CAPTURED" | grep -q "$1"; then
+		if printf '%s\n' "$CAPTURED" | grep -F -q "$1"; then
 			return 0
 		fi
 		sleep 0.2
@@ -68,15 +68,15 @@ wait_for()
 	fail "timed out waiting for '$1'"
 }
 
-# wait_count $marker $n
+# wait_count $row-marker $n
 #
-# Wait (up to ~10s) until exactly $n rendered lines contain $marker.
+# Wait (up to ~10s) until exactly $n rendered list rows contain $row-marker.
 wait_count()
 {
 	i=0
 	while [ "$i" -lt 50 ]; do
 		CAPTURED=$(capture)
-		c=$(echo "$CAPTURED" | grep -c "$1")
+		c=$(printf '%s\n' "$CAPTURED" | grep -F -c "$1")
 		[ "$c" -eq "$2" ] && return 0
 		sleep 0.2
 		i=$((i + 1))
@@ -131,10 +131,10 @@ exit_mode()
 #
 #	0 zzz  1 window 0  2 pane 0  3 pane 1  4 window 1  5 pane 0
 #	6 aaa  7 window 0  8 pane 0
-$TMUX new-session -d -s zzz -x 80 -y 24 || exit 1
-$TMUX split-window -t zzz:0 || exit 1
-$TMUX new-window -t zzz || exit 1
-$TMUX new-session -d -s aaa -x 80 -y 24 || exit 1
+$TMUX new-session -d -s zzz -x 80 -y 24 'cat' || exit 1
+$TMUX split-window -t zzz:0 'cat' || exit 1
+$TMUX new-window -t zzz 'cat' || exit 1
+$TMUX new-session -d -s aaa -x 80 -y 24 'cat' || exit 1
 
 $TMUX2 new-session -d -s out -x 80 -y 24 "$TMUX attach -t aaa" || exit 1
 wait_clients 1 || fail "no client attached to test server"
@@ -145,10 +145,12 @@ wait_clients 1 || fail "no client attached to test server"
 # regression - its two-pane window 0. aaa contributes exactly three lines
 # (session, window, pane).
 $TMUX choose-tree -t aaa:0 -F 'F1' -f '#{==:#{session_name},aaa}' || exit 1
-wait_count 'F1' 3
+wait_count ': F1' 3
 out=$CAPTURED
-echo "$out" | grep -q 'aaa: F1' || fail "aaa missing when filter matches it"
-echo "$out" | grep -q 'zzz: F1' && fail "zzz shown but no pane matches"
+printf '%s\n' "$out" | grep -F -q 'aaa: F1' || \
+	fail "aaa missing when filter matches it"
+printf '%s\n' "$out" | grep -F -q 'zzz: F1' && \
+	fail "zzz shown but no pane matches"
 exit_mode q
 
 # --- filter keeping only zzz ------------------------------------------------
@@ -156,10 +158,12 @@ exit_mode q
 # zzz contributes six lines (session, two windows, three panes); aaa must
 # disappear.
 $TMUX choose-tree -t aaa:0 -F 'F2' -f '#{==:#{session_name},zzz}' || exit 1
-wait_count 'F2' 6
+wait_count ': F2' 6
 out=$CAPTURED
-echo "$out" | grep -q 'zzz: F2' || fail "zzz missing when filter matches it"
-echo "$out" | grep -q 'aaa: F2' && fail "aaa shown but no pane matches"
+printf '%s\n' "$out" | grep -F -q 'zzz: F2' || \
+	fail "zzz missing when filter matches it"
+printf '%s\n' "$out" | grep -F -q 'aaa: F2' && \
+	fail "aaa shown but no pane matches"
 exit_mode q
 
 # --- filter matching a single pane ------------------------------------------
@@ -167,22 +171,28 @@ exit_mode q
 # Only pane 1 of zzz:0 matches, so the tree is exactly session zzz, window 0
 # and that pane; zzz:1 and all of aaa must disappear.
 $TMUX choose-tree -t aaa:0 -F 'F3' -f '#{==:#{pane_index},1}' || exit 1
-wait_count 'F3' 3
+wait_count ': F3' 3
 out=$CAPTURED
-echo "$out" | grep -q 'zzz: F3' || fail "zzz missing when its pane matches"
-echo "$out" | grep -q 'aaa: F3' && fail "aaa shown but no pane matches"
-echo "$out" | grep -q '1: F3' || fail "matching pane missing"
+printf '%s\n' "$out" | grep -F -q 'zzz: F3' || \
+	fail "zzz missing when its pane matches"
+printf '%s\n' "$out" | grep -F -q 'aaa: F3' && \
+	fail "aaa shown but no pane matches"
+printf '%s\n' "$out" | grep -F -q '1: F3' || \
+	fail "matching pane missing"
 exit_mode q
 
 # --- filter matching nothing ------------------------------------------------
 #
 # Everything is shown and the filter indicator reports no matches.
 $TMUX choose-tree -t aaa:0 -F 'F4' -f '#{==:#{session_name},nosuch}' || exit 1
-wait_count 'F4' 9
+wait_count ': F4' 9
 out=$CAPTURED
-echo "$out" | grep -q 'aaa: F4' || fail "aaa missing with no-match filter"
-echo "$out" | grep -q 'zzz: F4' || fail "zzz missing with no-match filter"
-echo "$out" | grep -q 'no matches' || fail "no matches indicator missing"
+printf '%s\n' "$out" | grep -F -q 'aaa: F4' || \
+	fail "aaa missing with no-match filter"
+printf '%s\n' "$out" | grep -F -q 'zzz: F4' || \
+	fail "zzz missing with no-match filter"
+printf '%s\n' "$out" | grep -F -q 'no matches' || \
+	fail "no matches indicator missing"
 exit_mode q
 
 # --- -h with the tree pane as the only match --------------------------------
@@ -191,28 +201,32 @@ exit_mode q
 # match, so session and window aaa stay listed: two lines, no pane line.
 $TMUX choose-tree -h -t aaa:0 -F 'F5' -f '#{==:#{session_name},aaa}' || \
 	exit 1
-wait_count 'F5' 2
-echo "$CAPTURED" | grep -q 'aaa: F5' || fail "aaa missing with -h"
+wait_count ': F5' 2
+printf '%s\n' "$CAPTURED" | grep -F -q 'aaa: F5' || \
+	fail "aaa missing with -h"
 exit_mode q
 
 # --- sort orders ------------------------------------------------------------
 #
 # By index zzz (created first) sorts first, by name aaa does, and -r reverses.
 $TMUX choose-tree -t aaa:0 -F 'F6' -O index || exit 1
-wait_count 'F6' 9
-echo "$CAPTURED" | grep 'F6' | head -1 | grep -q 'zzz: F6' || \
+wait_count ': F6' 9
+printf '%s\n' "$CAPTURED" | grep -F ': F6' | head -1 | \
+	grep -F -q 'zzz: F6' || \
 	fail "zzz not first with -O index"
 exit_mode q
 
 $TMUX choose-tree -t aaa:0 -F 'F7' -O name || exit 1
-wait_count 'F7' 9
-echo "$CAPTURED" | grep 'F7' | head -1 | grep -q 'aaa: F7' || \
+wait_count ': F7' 9
+printf '%s\n' "$CAPTURED" | grep -F ': F7' | head -1 | \
+	grep -F -q 'aaa: F7' || \
 	fail "aaa not first with -O name"
 exit_mode q
 
 $TMUX choose-tree -t aaa:0 -F 'F8' -O name -r || exit 1
-wait_count 'F8' 9
-echo "$CAPTURED" | grep 'F8' | head -1 | grep -q 'zzz: F8' || \
+wait_count ': F8' 9
+printf '%s\n' "$CAPTURED" | grep -F ': F8' | head -1 | \
+	grep -F -q 'zzz: F8' || \
 	fail "zzz not first with -O name -r"
 exit_mode q
 
@@ -221,33 +235,35 @@ exit_mode q
 # g moves to the top (session zzz); h collapses it, hiding its five children;
 # l expands it again.
 $TMUX choose-tree -t aaa:0 -F 'G1' -O index || exit 1
-wait_count 'G1' 9
+wait_count ': G1' 9
 $TMUX send-keys -t aaa:0 g h || fail "send-keys collapse failed"
-wait_count 'G1' 4
+wait_count ': G1' 4
 $TMUX send-keys -t aaa:0 l || fail "send-keys expand failed"
-wait_count 'G1' 9
+wait_count ': G1' 9
 exit_mode q
 
 # --- filter entered at the prompt with f, cleared with c ----------------------
 $TMUX choose-tree -t aaa:0 -F 'G2' -O index || exit 1
-wait_count 'G2' 9
+wait_count ': G2' 9
 $TMUX send-keys -t aaa:0 f || fail "send-keys f failed"
 $TMUX send-keys -t aaa:0 -l '#{==:#{session_name},aaa}' || \
 	fail "send-keys filter failed"
 $TMUX send-keys -t aaa:0 Enter || fail "send-keys Enter failed"
-wait_count 'G2' 3
+wait_count ': G2' 3
 out=$CAPTURED
-echo "$out" | grep -q 'aaa: G2' || fail "aaa missing with prompt filter"
-echo "$out" | grep -q 'zzz: G2' && fail "zzz shown with prompt filter"
+printf '%s\n' "$out" | grep -F -q 'aaa: G2' || \
+	fail "aaa missing with prompt filter"
+printf '%s\n' "$out" | grep -F -q 'zzz: G2' && \
+	fail "zzz shown with prompt filter"
 $TMUX send-keys -t aaa:0 c || fail "send-keys c failed"
-wait_count 'G2' 9
+wait_count ': G2' 9
 exit_mode q
 
 # --- Enter runs the default command (switch-client) ----------------------------
 #
 # g selects session zzz and Enter switches the client to it.
 $TMUX choose-tree -t aaa:0 -F 'G3' -O index || exit 1
-wait_count 'G3' 9
+wait_count ': G3' 9
 $TMUX send-keys -t aaa:0 g Enter || fail "send-keys Enter failed"
 i=0
 while [ "$i" -lt 50 ]; do
@@ -265,11 +281,11 @@ wait_mode aaa:0 0
 # g and four times j select window 1 of zzz; x asks for confirmation and y
 # kills it, leaving zzz with one window and the tree with seven lines.
 $TMUX choose-tree -t aaa:0 -F 'G4' -O index || exit 1
-wait_count 'G4' 9
+wait_count ': G4' 9
 $TMUX send-keys -t aaa:0 g j j j j x || fail "send-keys x failed"
 wait_for 'Kill window 1'
 $TMUX send-keys -t aaa:0 y || fail "send-keys y failed"
-wait_count 'G4' 7
+wait_count ': G4' 7
 [ "$($TMUX list-windows -t zzz -F x | grep -c x)" -eq 1 ] || \
 	fail "window 1 of zzz not killed"
 exit_mode q
diff --git a/regress/combine-test.sh b/regress/combine-test.sh
index a4d4f3681..ac9f800b0 100644
--- a/regress/combine-test.sh
+++ b/regress/combine-test.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/command-alias.sh b/regress/command-alias.sh
index 632e959a2..aae434cc0 100644
--- a/regress/command-alias.sh
+++ b/regress/command-alias.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new-session -d -sfoo || exit 1
diff --git a/regress/command-order.sh b/regress/command-order.sh
index 775768a6a..9c957246a 100644
--- a/regress/command-order.sh
+++ b/regress/command-order.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/conf-syntax.sh b/regress/conf-syntax.sh
index 49b9710b3..4dbc384b3 100644
--- a/regress/conf-syntax.sh
+++ b/regress/conf-syntax.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 for i in conf/*.conf; do
diff --git a/regress/control-client-sanity.sh b/regress/control-client-sanity.sh
index f6c36e1bd..32695e7c0 100644
--- a/regress/control-client-sanity.sh
+++ b/regress/control-client-sanity.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/control-client-size.sh b/regress/control-client-size.sh
index 7d5e1dc27..e6742608a 100644
--- a/regress/control-client-size.sh
+++ b/regress/control-client-size.sh
@@ -8,7 +8,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/control-subscriptions.sh b/regress/control-subscriptions.sh
index f720b0650..8aebb2ea0 100644
--- a/regress/control-subscriptions.sh
+++ b/regress/control-subscriptions.sh
@@ -7,7 +7,7 @@ LANG=C.UTF-8
 export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 TMPDIR=$(mktemp -d)
 IN="$TMPDIR/in"
diff --git a/regress/copy-mode-test-emacs.sh b/regress/copy-mode-test-emacs.sh
index a5b69c675..3e9cbf50b 100644
--- a/regress/copy-mode-test-emacs.sh
+++ b/regress/copy-mode-test-emacs.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new -d -x40 -y10 \
diff --git a/regress/copy-mode-test-vi.sh b/regress/copy-mode-test-vi.sh
index 2d6bfc287..71810b006 100644
--- a/regress/copy-mode-test-vi.sh
+++ b/regress/copy-mode-test-vi.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -f/dev/null -Ltest"
+TMUX="$TEST_TMUX -f/dev/null -LtestA$$"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new -d -x40 -y10 \
diff --git a/regress/cursor-test1.sh b/regress/cursor-test1.sh
index 73a336be7..b098cdc15 100644
--- a/regress/cursor-test1.sh
+++ b/regress/cursor-test1.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/cursor-test2.sh b/regress/cursor-test2.sh
index 3de80fdac..8e9e7ec80 100644
--- a/regress/cursor-test2.sh
+++ b/regress/cursor-test2.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/cursor-test3.sh b/regress/cursor-test3.sh
index e4881c79a..213ed83ba 100644
--- a/regress/cursor-test3.sh
+++ b/regress/cursor-test3.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/cursor-test4.sh b/regress/cursor-test4.sh
index 8f4dfa5c3..0eb5f0c9a 100644
--- a/regress/cursor-test4.sh
+++ b/regress/cursor-test4.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/decrqm-sync.sh b/regress/decrqm-sync.sh
index 7f8c3f61d..f4daf36a9 100644
--- a/regress/decrqm-sync.sh
+++ b/regress/decrqm-sync.sh
@@ -9,7 +9,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 sleep 1
 
diff --git a/regress/environ-update.sh b/regress/environ-update.sh
index 59f7d74c5..44e4e72c4 100644
--- a/regress/environ-update.sh
+++ b/regress/environ-update.sh
@@ -17,9 +17,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 # A second server on its own socket hosts the pane that runs the inner client.
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/environ.sh b/regress/environ.sh
index 244ec367d..2d5c0c031 100644
--- a/regress/environ.sh
+++ b/regress/environ.sh
@@ -19,7 +19,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_value $args $expected
@@ -151,7 +151,7 @@ cat > "$CONF" <<EOF
 CFGVAR=fromconfig
 %hidden CFGHID=hiddencfg
 EOF
-CTMUX="$TEST_TMUX -Ltest2 -f$CONF"
+CTMUX="$TEST_TMUX -LtestB$$ -f$CONF"
 $CTMUX kill-server 2>/dev/null
 $CTMUX new-session -d -s c -x 80 -y 24 || { rm -f "$CONF"; exit 1; }
 out=$($CTMUX show-environment -g CFGVAR 2>&1)
diff --git a/regress/floating-pane-geometry.sh b/regress/floating-pane-geometry.sh
index 7bd033ff6..7e80e8942 100644
--- a/regress/floating-pane-geometry.sh
+++ b/regress/floating-pane-geometry.sh
@@ -15,7 +15,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 fail()
diff --git a/regress/format-fuzzy.sh b/regress/format-fuzzy.sh
index 31a5b60cb..00bc28bd4 100644
--- a/regress/format-fuzzy.sh
+++ b/regress/format-fuzzy.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 # test_format $format $expected_result
 test_format()
diff --git a/regress/format-modifiers.sh b/regress/format-modifiers.sh
index 21203b6a9..b6340b622 100644
--- a/regress/format-modifiers.sh
+++ b/regress/format-modifiers.sh
@@ -17,7 +17,7 @@ LC_ALL=C.UTF-8
 export TZ LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 ESC=$(printf '\033')
 
diff --git a/regress/format-mouse.sh b/regress/format-mouse.sh
index 8032f8a57..9a443d19c 100644
--- a/regress/format-mouse.sh
+++ b/regress/format-mouse.sh
@@ -18,8 +18,8 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 cleanup()
 {
diff --git a/regress/format-render-contexts.sh b/regress/format-render-contexts.sh
index a91fb88e1..2cceff2e3 100644
--- a/regress/format-render-contexts.sh
+++ b/regress/format-render-contexts.sh
@@ -9,8 +9,8 @@ export PATH TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 
-TMUX="$TEST_TMUX -Lformat-render-contexts-$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Lformat-render-contexts-outer-$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 LIMIT=20000
 
 cleanup()
@@ -49,7 +49,13 @@ tmux_run()
 	name=$1
 	shift
 
-	out=$(run_cmd $TMUX "$@" 2>&1)
+	out=$(
+		if command -v timeout >/dev/null 2>&1; then
+			timeout 10 $TMUX "$@" 2>&1
+		else
+			$TMUX "$@" 2>&1
+		fi
+	)
 	rc=$?
 	bounded "$name" "$out"
 	[ "$rc" -eq 0 ] || fail "$name failed: $out"
@@ -58,7 +64,13 @@ tmux_run()
 
 capture()
 {
-	out=$(run_cmd $TMUX2 capture-pane -p -t out:0 2>/dev/null)
+	out=$(
+		if command -v timeout >/dev/null 2>&1; then
+			timeout 10 $TMUX2 capture-pane -p -t out:0 2>/dev/null
+		else
+			$TMUX2 capture-pane -p -t out:0 2>/dev/null
+		fi
+	)
 	rc=$?
 	bounded "capture-pane" "$out"
 	[ "$rc" -eq 0 ] || fail "capture-pane failed"
@@ -67,7 +79,14 @@ capture()
 
 capture_esc()
 {
-	out=$(run_cmd $TMUX2 capture-pane -pe -t out:0 2>/dev/null)
+	out=$(
+		if command -v timeout >/dev/null 2>&1; then
+			timeout 10 $TMUX2 capture-pane -pe -t out:0 \
+				2>/dev/null
+		else
+			$TMUX2 capture-pane -pe -t out:0 2>/dev/null
+		fi
+	)
 	rc=$?
 	bounded "capture-pane -e" "$out"
 	[ "$rc" -eq 0 ] || fail "capture-pane -e failed"
diff --git a/regress/format-strings.sh b/regress/format-strings.sh
index bae66ab00..877e18fec 100644
--- a/regress/format-strings.sh
+++ b/regress/format-strings.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 # test_format $format $expected_result
 test_format()
diff --git a/regress/format-variables.sh b/regress/format-variables.sh
index fa51e0216..9131c2cf4 100644
--- a/regress/format-variables.sh
+++ b/regress/format-variables.sh
@@ -15,10 +15,10 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 # A second server on its own socket provides a real terminal (an inner client
 # attached inside one of its panes) so client terminal variables are populated.
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 # Every variable name in format_table[].  Kept as a plain word list so it can be
 # iterated with normal shell word splitting.
diff --git a/regress/has-session-return.sh b/regress/has-session-return.sh
index a7d76ad85..8b259ac76 100644
--- a/regress/has-session-return.sh
+++ b/regress/has-session-return.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX -f/dev/null has -tfoo </dev/null 2>/dev/null && exit 1
diff --git a/regress/hooks-after.sh b/regress/hooks-after.sh
index 605109570..3c1ba7909 100644
--- a/regress/hooks-after.sh
+++ b/regress/hooks-after.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/hooks-lifecycle.sh b/regress/hooks-lifecycle.sh
index 6fb271131..e90f7ba3a 100644
--- a/regress/hooks-lifecycle.sh
+++ b/regress/hooks-lifecycle.sh
@@ -15,7 +15,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/hooks-notify.sh b/regress/hooks-notify.sh
index 947dd6c68..41916248c 100644
--- a/regress/hooks-notify.sh
+++ b/regress/hooks-notify.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/hooks.sh b/regress/hooks.sh
index 537582295..e1d75bf67 100644
--- a/regress/hooks.sh
+++ b/regress/hooks.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/if-shell-TERM.sh b/regress/if-shell-TERM.sh
index 21846fd10..d1db52f45 100644
--- a/regress/if-shell-TERM.sh
+++ b/regress/if-shell-TERM.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/if-shell-error.sh b/regress/if-shell-error.sh
index 2eab8f7ca..3b2dac753 100644
--- a/regress/if-shell-error.sh
+++ b/regress/if-shell-error.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/if-shell-nested.sh b/regress/if-shell-nested.sh
index 434775c43..e10be41c6 100644
--- a/regress/if-shell-nested.sh
+++ b/regress/if-shell-nested.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/input-common.inc b/regress/input-common.inc
index 96eec1f09..100a7be0f 100644
--- a/regress/input-common.inc
+++ b/regress/input-common.inc
@@ -2,7 +2,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 TMP=$(mktemp)
 EXP=$(mktemp)
diff --git a/regress/input-keys.sh b/regress/input-keys.sh
index e2fc41f54..cb771d19a 100644
--- a/regress/input-keys.sh
+++ b/regress/input-keys.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 sleep 1
 $TMUX -f/dev/null new -x20 -y2 -d \; set -g escape-time 0 || exit 1
diff --git a/regress/input-reflow-stress.sh b/regress/input-reflow-stress.sh
index aa1bbd717..926e8cdd0 100644
--- a/regress/input-reflow-stress.sh
+++ b/regress/input-reflow-stress.sh
@@ -8,8 +8,8 @@ export PATH TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 
-TMUX="$TEST_TMUX -Linput-reflow-stress-$$ -f/dev/null"
-TMUX2="$TEST_TMUX -Linput-reflow-stress-outer-$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 TMP=$(mktemp "${TMPDIR:-/tmp}/input-reflow-stress.XXXXXX") || exit 1
 EXP=$(mktemp "${TMPDIR:-/tmp}/input-reflow-stress.XXXXXX") || exit 1
diff --git a/regress/input-replies.sh b/regress/input-replies.sh
index 3435cd943..5fc77f843 100644
--- a/regress/input-replies.sh
+++ b/regress/input-replies.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 $TMUX kill-server 2>/dev/null
 sleep 0.5
diff --git a/regress/input-requests.sh b/regress/input-requests.sh
index 5e7b3781a..094ce2a8a 100644
--- a/regress/input-requests.sh
+++ b/regress/input-requests.sh
@@ -15,7 +15,8 @@ import tempfile
 import time
 
 tmux = sys.argv[1]
-server = [tmux, "-Ltest", "-f/dev/null"]
+label = "testA%d" % os.getpid()
+server = [tmux, "-L" + label, "-f/dev/null"]
 
 def run(*args, check=True):
     return subprocess.run(server + list(args), check=check,
@@ -25,7 +26,7 @@ def attach():
     pid, fd = os.forkpty()
     if pid == 0:
         os.environ["TERM"] = "xterm-256color"
-        os.execl(tmux, tmux, "-Ltest", "-f/dev/null", "attach-session",
+        os.execl(tmux, tmux, "-L" + label, "-f/dev/null", "attach-session",
             "-t", "requests")
     os.set_blocking(fd, False)
     return pid, fd
diff --git a/regress/kill-session-process-exit.sh b/regress/kill-session-process-exit.sh
index 04617ca2c..405449be2 100644
--- a/regress/kill-session-process-exit.sh
+++ b/regress/kill-session-process-exit.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 sleep 1
 
diff --git a/regress/lifecycle-deferred.sh b/regress/lifecycle-deferred.sh
index 2650f1827..d2669ff46 100644
--- a/regress/lifecycle-deferred.sh
+++ b/regress/lifecycle-deferred.sh
@@ -8,8 +8,8 @@ export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
 
-TMUX="$TEST_TMUX -Llifecycle-deferred -f/dev/null"
-TMUX2="$TEST_TMUX -Llifecycle-deferred-outer -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 TMPDIR=$(mktemp -d)
 IN="$TMPDIR/in"
diff --git a/regress/mode-mutation.sh b/regress/mode-mutation.sh
index cab8e72c8..96927e995 100644
--- a/regress/mode-mutation.sh
+++ b/regress/mode-mutation.sh
@@ -8,20 +8,30 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
+TMP=$(mktemp -d) || exit 1
+TMUX_TMPDIR="$TMP"
+export TMUX_TMPDIR
 
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
-cleanup()
+cleanup_servers()
 {
 	$TMUX kill-server 2>/dev/null
 	$TMUX2 kill-server 2>/dev/null
 	sleep 0.5
 }
 
+cleanup()
+{
+	cleanup_servers
+	rm -rf "$TMP"
+}
+trap cleanup EXIT
+
 fail()
 {
-	echo "$1"
+	echo "$1" >&2
 	cleanup
 	exit 1
 }
@@ -53,7 +63,7 @@ wait_for()
 {
 	i=0
 	while [ "$i" -lt 50 ]; do
-		capture | grep -q "$1" && return 0
+		capture | grep -F -q "$1" && return 0
 		sleep 0.2
 		i=$((i + 1))
 	done
@@ -95,7 +105,7 @@ start_client()
 	s=$1
 	cmd=${2:-cat}
 
-	cleanup
+	cleanup_servers
 	$TMUX new-session -d -s "$s" -n main -x 80 -y 24 "$cmd" || \
 		fail "$s: new-session failed"
 	$TMUX2 new-session -d -s out -x 80 -y 24 "$TMUX attach -t $s" || \
@@ -287,7 +297,7 @@ test_copy_mode()
 	assert_alive "copy-mode exit"
 }
 
-cleanup
+cleanup_servers
 test_choose_tree
 test_choose_buffer
 test_choose_client
diff --git a/regress/new-session-base-index.sh b/regress/new-session-base-index.sh
index bb6dd5945..89fdb4de5 100644
--- a/regress/new-session-base-index.sh
+++ b/regress/new-session-base-index.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-session-command.sh b/regress/new-session-command.sh
index b2fc91db7..520c91e4f 100644
--- a/regress/new-session-command.sh
+++ b/regress/new-session-command.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-session-environment.sh b/regress/new-session-environment.sh
index e5404e67d..fc935687f 100644
--- a/regress/new-session-environment.sh
+++ b/regress/new-session-environment.sh
@@ -5,7 +5,7 @@
 PATH=/bin:/usr/bin
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TERM=$($TMUX start \; show -gv default-terminal)
diff --git a/regress/new-session-no-client.sh b/regress/new-session-no-client.sh
index 84fddaecb..2f3da5abe 100644
--- a/regress/new-session-no-client.sh
+++ b/regress/new-session-no-client.sh
@@ -8,7 +8,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-session-size.sh b/regress/new-session-size.sh
index 029bd6eed..6a35abbbd 100644
--- a/regress/new-session-size.sh
+++ b/regress/new-session-size.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/new-window-command.sh b/regress/new-window-command.sh
index 183491159..21a2661e8 100644
--- a/regress/new-window-command.sh
+++ b/regress/new-window-command.sh
@@ -6,7 +6,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/options-array.sh b/regress/options-array.sh
index 3b18ce977..c372e3461 100644
--- a/regress/options-array.sh
+++ b/regress/options-array.sh
@@ -20,7 +20,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 check_value()
diff --git a/regress/options-scope.sh b/regress/options-scope.sh
index bbc7168aa..ac6d62f77 100644
--- a/regress/options-scope.sh
+++ b/regress/options-scope.sh
@@ -17,7 +17,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_value $args $expected
diff --git a/regress/options-values.sh b/regress/options-values.sh
index 28acd2b47..75da52e01 100644
--- a/regress/options-values.sh
+++ b/regress/options-values.sh
@@ -17,7 +17,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 check_value()
diff --git a/regress/osc-11colours.sh b/regress/osc-11colours.sh
index 2fba76d82..5cdc1be41 100644
--- a/regress/osc-11colours.sh
+++ b/regress/osc-11colours.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 $TMUX new -d
diff --git a/regress/pane-ops.sh b/regress/pane-ops.sh
index 46984bc27..762bea200 100644
--- a/regress/pane-ops.sh
+++ b/regress/pane-ops.sh
@@ -30,7 +30,7 @@ LC_ALL=C.UTF-8
 export TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_ok $cmd...
diff --git a/regress/prompt-keys.sh b/regress/prompt-keys.sh
index 8c17581b1..6fde51b7b 100644
--- a/regress/prompt-keys.sh
+++ b/regress/prompt-keys.sh
@@ -7,8 +7,8 @@ LANG=C.UTF-8
 export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-OUT="$TEST_TMUX -Ltest -f/dev/null"		# outer (host for the client)
-IN="$TEST_TMUX -Ltest2 -f/dev/null"		# inner (under test)
+OUT="$TEST_TMUX -LtestA$$ -f/dev/null"		# outer (host for the client)
+IN="$TEST_TMUX -LtestB$$ -f/dev/null"		# inner (under test)
 
 $OUT kill-server 2>/dev/null
 $IN kill-server 2>/dev/null
diff --git a/regress/prompt-mechanics.sh b/regress/prompt-mechanics.sh
index 6f3e5294e..55bd17a69 100644
--- a/regress/prompt-mechanics.sh
+++ b/regress/prompt-mechanics.sh
@@ -20,8 +20,8 @@ LANG=C.UTF-8
 export TERM LC_ALL LANG
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-OUT="$TEST_TMUX -Ltest -f/dev/null"		# outer (host for the client)
-IN="$TEST_TMUX -Ltest2 -f/dev/null"		# inner (under test)
+OUT="$TEST_TMUX -LtestA$$ -f/dev/null"		# outer (host for the client)
+IN="$TEST_TMUX -LtestB$$ -f/dev/null"		# inner (under test)
 
 $OUT kill-server 2>/dev/null
 $IN kill-server 2>/dev/null
diff --git a/regress/run-shell-output.sh b/regress/run-shell-output.sh
index 3b44504c2..926a520c9 100644
--- a/regress/run-shell-output.sh
+++ b/regress/run-shell-output.sh
@@ -7,7 +7,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-bidi.sh b/regress/screen-redraw-bidi.sh
index e4e962950..ee9c2fa16 100644
--- a/regress/screen-redraw-bidi.sh
+++ b/regress/screen-redraw-bidi.sh
@@ -17,8 +17,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-cache.sh b/regress/screen-redraw-cache.sh
index 27c98e3b4..0e0abf9db 100644
--- a/regress/screen-redraw-cache.sh
+++ b/regress/screen-redraw-cache.sh
@@ -18,8 +18,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-floating.sh b/regress/screen-redraw-floating.sh
index 82c36d364..67d213699 100644
--- a/regress/screen-redraw-floating.sh
+++ b/regress/screen-redraw-floating.sh
@@ -16,8 +16,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-indicators.sh b/regress/screen-redraw-indicators.sh
index 60bf652b2..28a1dee6c 100644
--- a/regress/screen-redraw-indicators.sh
+++ b/regress/screen-redraw-indicators.sh
@@ -18,8 +18,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-outside.sh b/regress/screen-redraw-outside.sh
index 53a2a72b1..3eeb94938 100644
--- a/regress/screen-redraw-outside.sh
+++ b/regress/screen-redraw-outside.sh
@@ -18,8 +18,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-popups.sh b/regress/screen-redraw-popups.sh
index 1eb7e5897..8ad3ba2eb 100644
--- a/regress/screen-redraw-popups.sh
+++ b/regress/screen-redraw-popups.sh
@@ -17,8 +17,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-scrollbars.sh b/regress/screen-redraw-scrollbars.sh
index f8298b5e1..914fe542c 100644
--- a/regress/screen-redraw-scrollbars.sh
+++ b/regress/screen-redraw-scrollbars.sh
@@ -16,8 +16,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-status.sh b/regress/screen-redraw-status.sh
index 12ca20bb1..46cb5fcad 100644
--- a/regress/screen-redraw-status.sh
+++ b/regress/screen-redraw-status.sh
@@ -20,8 +20,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-tiled.sh b/regress/screen-redraw-tiled.sh
index 94353f5f8..3b32478f0 100644
--- a/regress/screen-redraw-tiled.sh
+++ b/regress/screen-redraw-tiled.sh
@@ -24,8 +24,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/screen-redraw-window-style.sh b/regress/screen-redraw-window-style.sh
index 1d2b2b281..69ac824f2 100644
--- a/regress/screen-redraw-window-style.sh
+++ b/regress/screen-redraw-window-style.sh
@@ -13,8 +13,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 RESULTS=screen-redraw-results
 
 TMP=$(mktemp)
diff --git a/regress/session-group-resize.sh b/regress/session-group-resize.sh
index 28e7a85ed..f2b634a43 100644
--- a/regress/session-group-resize.sh
+++ b/regress/session-group-resize.sh
@@ -10,7 +10,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 TMP1=$(mktemp)
diff --git a/regress/session-ops.sh b/regress/session-ops.sh
index 4938ee22c..08c5dfbae 100644
--- a/regress/session-ops.sh
+++ b/regress/session-ops.sh
@@ -27,7 +27,7 @@ LC_ALL=C.UTF-8
 export TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_ok $cmd...
diff --git a/regress/set-hook-B.sh b/regress/set-hook-B.sh
index 188bfdd24..4947af70c 100644
--- a/regress/set-hook-B.sh
+++ b/regress/set-hook-B.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/set-hook-R.sh b/regress/set-hook-R.sh
index b36edc323..49af68efc 100644
--- a/regress/set-hook-R.sh
+++ b/regress/set-hook-R.sh
@@ -10,7 +10,7 @@ export TERM LC_ALL LANG
 OUT=$(mktemp -d)
 TMUX_TMPDIR="$OUT"
 export TMUX_TMPDIR
-TMUX="$TEST_TMUX -Ltest$$ -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 
 fail()
 {
diff --git a/regress/style-trim.sh b/regress/style-trim.sh
index 5b03482d9..f42e0ffff 100644
--- a/regress/style-trim.sh
+++ b/regress/style-trim.sh
@@ -17,9 +17,9 @@ if command -v bash >/dev/null 2>&1; then
 fi
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX2 kill-server 2>/dev/null
 
 $TMUX2 -f/dev/null new -d "$TMUX -f/dev/null new -- $shell"
diff --git a/regress/targets-panes.sh b/regress/targets-panes.sh
index db353403b..9ea936173 100644
--- a/regress/targets-panes.sh
+++ b/regress/targets-panes.sh
@@ -27,7 +27,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check $target $expected [format]
diff --git a/regress/targets.sh b/regress/targets.sh
index 346a86736..75ee3dbb8 100644
--- a/regress/targets.sh
+++ b/regress/targets.sh
@@ -29,7 +29,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check $target $expected [format]
diff --git a/regress/tty-draw-line.sh b/regress/tty-draw-line.sh
index b57de08cc..59331aa0d 100644
--- a/regress/tty-draw-line.sh
+++ b/regress/tty-draw-line.sh
@@ -10,8 +10,8 @@ LC_ALL=C.UTF-8
 export TERM LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 
 fail() {
 	echo "$*" >&2
diff --git a/regress/tty-keys.sh b/regress/tty-keys.sh
index 849f6f336..1b300b995 100644
--- a/regress/tty-keys.sh
+++ b/regress/tty-keys.sh
@@ -4,9 +4,9 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
-TMUX2="$TEST_TMUX -Ltest2 -f/dev/null"
+TMUX2="$TEST_TMUX -LtestB$$ -f/dev/null"
 $TMUX2 kill-server 2>/dev/null
 
 TMP=$(mktemp)
diff --git a/regress/utf8-test.sh b/regress/utf8-test.sh
index b3cf41bd0..1836cc459 100644
--- a/regress/utf8-test.sh
+++ b/regress/utf8-test.sh
@@ -4,7 +4,7 @@ PATH=/bin:/usr/bin
 TERM=screen
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 TMP=$(mktemp)
 trap "rm -f $TMP" 0 1 15
 $TMUX kill-server 2>/dev/null
diff --git a/regress/window-ops.sh b/regress/window-ops.sh
index dde7fc957..bdb1b5fb9 100644
--- a/regress/window-ops.sh
+++ b/regress/window-ops.sh
@@ -30,7 +30,7 @@ LC_ALL=C.UTF-8
 export TERM LANG LC_ALL
 
 [ -z "$TEST_TMUX" ] && TEST_TMUX=$(readlink -f ../tmux)
-TMUX="$TEST_TMUX -Ltest -f/dev/null"
+TMUX="$TEST_TMUX -LtestA$$ -f/dev/null"
 $TMUX kill-server 2>/dev/null
 
 # check_ok $cmd...